Treadmill belt with foamed cushion layer and method of making

ABSTRACT

The present invention is directed to a treadmill belt with foamed cushion layer and method of making same. In one embodiment, the treadmill belt includes a fabric base layer and a foamed cushion layer foamed on and integral with the fabric base layer. The foamed cushion layer includes a thermoplastic composition and has a Shore A hardness of about 20 to about 80. In one example, the first foamed cushion layer is from about 0.05 inches to about 0.35 inches thick. The thermoplastic composition, prior to being foamed, includes about 1 part to about 5 parts of a foaming agent, e.g., a chemical foaming agent, based on 100 parts thermoplastic material, e.g., polyvinyl chloride. An outer wear layer is securely adhered on the foamed cushion layer to sandwich the foamed cushion layer between the fabric base layer and outer wear layer thereby defining the treadmill belt.

This is a divisional and continuation-in-part of U.S. patent applicationSer. No. 11/970,870, filed on Jan. 8, 2008. The teachings of U.S. patentapplication Ser. No. 11/970,870 are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

The present invention is directed to a treadmill belt with foamedcushion layer and method of making same.

BACKGROUND OF THE INVENTION

Treadmills have long been a favorite stationary means for exercising. Atypical treadmill includes an elongated platform with multiple rollers.A continuous treadmill belt longitudinally encircles the platformresting on the rollers. Handrails extend upward from the front of theplatform for providing stability to a user on the treadmill. Whilewalking or running on the treadmill belt, the user can grip thehandrails. The treadmill belt can be either motorized or rotate underthe force of the user. In either case, the treadmill belt rotates on therollers in a continuous circular fashion as the user runs or walks onthe treadmill belt. This process continues until the user reaches adesired level of exercise.

Because typical treadmill platforms tend to provide a stiff, hardrunning surface which can become uncomfortable to the user over extendedperiods of running, some manufacturers have applied a resilient coatingto the running surface, such as rubber or carpeting, to reduce footimpact. However, these surfaces have not provided the desired level ofcomfort or durability because the running surface tends to retain itsinherent stiffness and insufficiently resists the impact and shearingforces that are applied to the belt as the user moves thereon. Attemptsto solve these problems, such as by using a thicker belt to provide amore shock absorbent running surface, have not been successful. Thethicker the belt, the more power that is required to drive the pulley.Thus, to keep motor size cost effective, it has been necessary to keepthe belt relatively thin. While attempts have been made to produce thin,cushioned treadmill belts, effective belts that can be easilymanufactured and withstand the required impact and stresses, yet,provide cushioning have not been produced.

Accordingly, there is a need for a treadmill belt with a cushioned layerthat is easy to manufacture, not too thick, and provides the neededdurability and shock absorbing characteristics to help prevent injury tothe runner.

SUMMARY OF THE INVENTION

The present invention is directed to a treadmill belt with foamedcushion layer and method of making same.

In one embodiment, the treadmill belt includes a fabric base layer and afoamed cushion layer foamed on and integral with the fabric base layer.The foamed cushion layer includes a thermoplastic composition and has aShore A hardness of about 20 to about 80. In one example, the foamedcushion layer is from about 0.05 inches to about 0.35 inches thick. Thethermoplastic composition, prior to being foamed, includes about 1 partto about 5 parts of a foaming agent, e.g., a chemical foaming agent,based on 100 parts thermoplastic material, e.g., polyvinyl chloride. Anouter wear layer is securely adhered on the foamed cushion layer so asto sandwich the foamed cushion layer between the fabric base layer andouter wear layer thereby defining the treadmill belt with foamed cushionlayer.

The treadmill belt, in one embodiment, can be formed by applying atleast one layer of an unfoamed thermoplastic composition on a fabricbase layer. In one example, the unfoamed thermoplastic compositionincludes a chemical foaming agent in an amount of about 1 part to about5 parts chemical foaming agent, such as an azo compound, based on 100parts thermoplastic material, such as polyvinyl chloride. Next, theunfoamed thermoplastic composition is foamed, such as by being heated,to define a foamed cushion layer which has a Shore A hardness of about20 to about 80. Then, an outer wear layer is applied on the foamedcushion layer to define the treadmill belt with foamed cushion layer.

By virtue of the foregoing, there is provided a treadmill belt withfoamed cushion layer that is easy to manufacture, not too thick, andprovides the needed durability and shock absorbing characteristics tohelp prevent injury to the runner.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the general description of the invention given above, anddetailed description given below, serve to explain the invention.

FIG. 1 is a perspective view of a treadmill having a treadmill belt withfoamed cushion layer;

FIG. 2 is a cross-sectional view of a length of the treadmill belt ofFIG. 1;

FIG. 2A is a cross-sectional view of an alternate embodiment of thetreadmill belt of FIG. 2; and

FIGS. 3-5 illustrate a process of making the treadmill belt of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows a treadmill 10 including a treadmill belt 12 that iscontinuous and rotatably mounted on rollers (not shown). The treadmillbelt 12 can be motorized for automatic rotation or rotated by forcesupplied by the user. As the user walks or runs, the treadmill belt 12rotates, thereby allowing the user to continue to run or walk thereonwhile maintaining a relatively stationary position.

With reference to FIG. 2, the treadmill belt 12, in one embodiment,includes a fabric base layer 14 that defines an interior surface 16 ofthe treadmill belt 12. The treadmill belt 12 further includes a foamedcushion layer 20 foamed on and integral with the fabric base layer 14,as further explained below. The foamed cushion layer 20 includes afoamed thermoplastic composition. While shown in FIG. 2 as being foameddirectly onto and integral with fabric base layer 14, it is understoodthat other conventional layers, as known in the art, may be situatedbetween the foamed cushion layer 20 and fabric base layer 14.

An outer wear layer 22, which defines a running surface 24 for the user,is securely adhered, such as by heat bonding, on the foamed cushionlayer 20 so as to sandwich the foamed cushion layer 20 between thefabric base layer 14 and outer wear layer 22, thereby defining thetreadmill belt 12. And, while shown in FIG. 2 as being securely adhereddirectly to the foamed cushion layer 20, it is understood that otherconventional layers, as known in the art, may be situated between theouter wear layer 22 and the foamed cushion layer 20.

The fabric base layer 14 of the treadmill belt 12 rides on and pressesagainst the rollers during rotation of the treadmill belt 12. Inaddition, the fabric base layer 14 can withstand the localized forcesapplied to the treadmill belt 12 as a result of a user running thereon.Those forces can be as high as 400-600 pounds per square inch. Thematerial for the fabric base layer 14 is substantially non-extendable soas to prevent the treadmill belt 12 from slipping on the rollers. Thefabric base layer 14 also may include either a one-ply or multi-plysheet of woven fabric. Such woven fabric includes synthetic and/ornatural fibers, such as polyester, nylon, rayon, and/or cotton. Thefibers may be provided as mono- or multi-filament or spun yarns. In oneexample, the woven fabric includes a multi-filament polyester.

The foamed thermoplastic composition of the foamed cushion layer 20 isresiliently compressible. The foamed thermoplastic composition layer isa solid material which has a Shore A hardness of about 20 to about 80 soas to provide a desirable flexibility. In another example, the foamedthermoplastic composition has a Shore A hardness of about 30 to about50. The foamed thermoplastic composition is typically free of semi-solidsubstances, such as epoxidized vegetable oil.

Prior to being foamed, the thermoplastic composition, also referred toherein as the unfoamed thermoplastic composition, includes 100 partsthermoplastic material and about 1 part to about 5 parts of a foaming,or blowing, agent based on 100 parts thermoplastic material. In oneexample, about 3 parts of foaming agent based on 100 parts thermoplasticmaterial is included in the unfoamed thermoplastic composition. Inaddition, plasticizers and other typical additives, such as stabilizers,oils, foaming catalysts, and the like, generally may be included inconventional amounts.

The thermoplastic material can include, for example, polyvinyl chloride,ethylene vinyl acetate, and/or polystyrene. In one example, thethermoplastic material is polyvinyl chloride. One such suitablepolyvinyl chloride is 68GP, which is a polyvinyl chloride dispersionresin available from Petco of Bogota, Colombia.

Foaming, or blowing, agents may be classified as physical and chemicalfoaming agents. Physical foaming agents do not undergo chemical changesduring processing and typically are provided in the form of compressedgas, e.g., nitrogen or carbon dioxide gas. Physical foaming agentscreate cellular structures in the unfoamed thermoplastic compositionwhen introduced into the unfoamed thermoplastic composition therebyfoaming the unfoamed composition.

Chemical foaming agents are mainly solids. These solids generally aremixed with the thermoplastic material. The chemical foaming agentscommonly release gases such as nitrogen, carbon dioxide, carbonmonoxide, or ammonia when heated. Thus, the unfoamed thermoplasticcomposition can be heated to the activation temperature of the chemicalfoaming agent to activate the foaming agent. The activated chemicalfoaming agent releases gases upon decomposition to create cellularstructures in the unfoamed thermoplastic composition, thereby foamingthe unfoamed composition. The chemical foaming agent can include an azocompound, such as azodicarbonamide, a hydrazine compound, a carbazide, atetrazole, a nitroso compound, and/or a carbonate, such as sodiumbicarbonate. In one example, the chemical foaming agent is an azocompound, e.g., azodicarbonamide. One such suitable azodicarbonamidefoaming agent is Celogen® AZ available from Chemtura Corporation ofMiddlebury, Conn.

The plasticizer can include, for example, dialkyl adipate esters,dialkyl azelates, glycol dibenzoate esters, epoxy derivatives includingepoxidized soybean oil, epoxidized tall oil and epoxy resins,glycollates such as butyl phthalyl, butyl glycollate, mellitates such astrialkyl trimellitates, phenoxy compounds, phosphate esters includingtriaryl, trialkyl and alkyl-aryl combinations, derivatives ofortho-phthalic acid such as dialkyl and alkyl benzyl o-phthalates,polyesters and dibasic acids with glycols (e.g., adipic, azelaic andphthalic acids with various glycols terminated with a monofunctionalcompound), and pentaerythritol derivatives and sulfonamides. In oneexample, the plasticizer is diisononyl phthalate.

In one non-limiting example, the unfoamed thermoplastic compositionincludes the following:

TABLE 1 Ingredient phr Polyvinyl chloride ¹ 100 Plasticizer ² 80 Calciumstabilizer ³ 2 Epoxidized soybean oil ⁴ 5 Chemical Foaming agent ⁵ 3 ¹68GP, which is a polyvinyl chloride dispersion resin available fromPetco of Bogota, Colombia. ² Diisononyl phthalate (DINP), which isavailable from BASF of Ludwigshafen, Germany. ³ Available from Ferro ofCleveland, Ohio. ⁴ Available from Ferro of Cleveland, Ohio ⁵ Celogen ®AZ, which is an azodicarbonamide available from Chemtura Corporation ofMiddlebury, Connecticut.

The foamed cushion layer 20 can be from about 0.05 inches to about 0.35inches thick. In one example, the foamed cushion layer 20 is about 0.180inches thick. The foamed cushion layer 20 typically has surfaces whichare exposed on the edges of both sides of the belt. This is also thecase with respect to the second foamed cushion layer 30 utilized in thealternative embodiment of this invention. In other words, the edges ofthe foamed cushion layer(s) are not covered with another material orlayer of material and are a part of the outer edges of the belt. Put isstill another way, the foamed cushion layer (or layers in the case ofthe alternative embodiment of this invention) are not contained withinthe structure of the belt by another layer or layers of material.

The outer wear layer 22 defines the running surface 24 on which the userwalks or runs and has a desirable durability. The outer wear layer 22can include a thermoplastic material or a rubber material. In oneexample, the thermoplastic material is a thermoplastic elastomer. Inanother example, the thermoplastic material includes polyvinyl chlorideor polyurethane. The rubber material can include conventional naturaland/or synthetic rubbers known in the art.

In an alternate embodiment, a bottom surface layer (not shown) may besecured to the underside of the fabric base layer 14 of the treadmillbelt 12. The bottom layer can include a thermoplastic material, whichprovides a low coefficient of friction. In one example, thethermoplastic material includes polyvinyl chloride, polyurethane, or apolyamide, such as nylon.

The total thickness of the treadmill belt 12 is from about 0.100 inchesto about 0.400 inches. In one example, the total thickness of thetreadmill belt 12 is about 0.200 inches. Another embodiment of thetreadmill belt 12 is best shown in FIG. 2A. In this embodiment, a fabricintermediate layer 28 is securely adhered directly to foamed cushionlayer 20, such as upon foaming or via heat bonding, so as to sandwichthe foamed cushion layer 20 between the fabric base layer 14 and fabricintermediate layer 28. Like foamed cushion layer 20, a second foamedcushion layer 30, which includes a thermoplastic composition, is foameddirectly onto and integral with the fabric intermediate layer 28, asexplained further below. It should be understood that additionalintermediate and foamed cushion layers 28 and 20, 30 may be similarlyalternately layered within treadmill belt 12, as desired, therebyproviding additional fabric layers.

Next, the outer wear layer 22 is securely adhered, such as by heatbonding, directly to the second foamed cushion layer 30 so as tosandwich the second foamed cushion layer 30 between the fabricintermediate layer 28 and outer wear layer 22, thereby defining thetreadmill belt 12 with first and second foamed cushion layers 20, 30. Inan alternate embodiment, foamed cushion layer 20 may be replaced with anunfoamed conventional layer (not shown), such unfoamed layer can includea conventional thermoplastic layer. The thermoplastic layer can includea thermoplastic composition, such as a polyvinyl chloride composition.Accordingly, for belts 12 with multiple fabric layers, as shown in FIG.2A, it should be understood that either standard thermoplastic layers orfoamed cushion layers can be provided between the fabric layers 14, 28,with at least one of those layers being a foamed cushion layer. In oneexample, the foamed cushion layer is closest to the outer wear layer 22.Also, as mentioned above, other conventional layers, as known in theart, may be situated between the various layers 14, 20, 22, 28, and 30.

Like the fabric base layer 14, the material for the fabric intermediatelayer 28 is substantially non-extendable. In one embodiment, the fabricintermediate layer 28 includes a one-ply or multi-ply sheet of wovenfabric. The woven fabric includes synthetic and/or natural fibers, suchas polyester, nylon, rayon, and/or cotton. The fibers may be provided asmono- or multi-filament or spun yarns. In one example, the woven fabricincludes a multi-filament polyester. The type of material used for thefabric intermediate layer 28 and the fabric base layer 14 is generallyinterchangeable and may be the same or different.

The foamed thermoplastic composition of the second foamed cushion layer30 is the same as that described above for foamed cushion layer 20. Theunfoamed thermoplastic compositions for the second foamed cushion layer30 and foamed cushion layer 20 may be the same or different in thetreadmill belt 12.

FIGS. 3-5 illustrate an embodiment of a method of making the treadmillbelt 12 of FIG. 2. With specific reference to FIG. 3, the methodincludes applying a layer 32 of the unfoamed thermoplastic compositionto the fabric base layer 14 using techniques known in the art, e.g., viaextrusion techniques. In another example, multiple layers of theunfoamed thermoplastic composition can be applied to the base fabriclayer 12. Next, the unfoamed thermoplastic composition is foamed using afoaming agent to create cellular structures in the unfoamedthermoplastic composition thereby defining the foamed cushion layer 20.Such foaming may occur by way of a physical or chemical foaming agent asis known in the art. When a chemical foaming agent is used, heating tothe activation temperature of the chemical foaming agent takes place. Asshown in FIG. 4, the resulting foamed cushion layer 20 is integral withthe fabric base layer 14.

By way of example, the unfoamed thermoplastic composition can includethe polyvinyl chloride composition of Table 1. That unfoamedcomposition, which includes an azidocarbamide foaming agent, is heated,as depicted by wavy lines 34, e.g., between about 300° F. to about 450°F., to activate and decompose the foaming agent. The decomposing agentreleases nitrogen gas to create cellular structures in the unfoamedcomposition thereby foaming the polyvinyl chloride compound. Asdiscussed above, the resulting foamed cushion layer 20 has a Shore Ahardness of about 20 to about 80 and is resiliently compressible andflexible. In addition, the integral fabric base layer 14, in oneexample, is a one-ply woven sheet of multifilament polyester.

With reference now to FIG. 5, after foaming of the unfoamedthermoplastic composition, the integral foamed cushion layer 20 andfabric base layer 14 are reheated, as depicted by wavy lines 36, to atemperature sufficient to heat bond and, thus, securely adhere the outerwear layer 22 to the foamed cushion layer 20. In one example, the outerwear layer 22 includes polyvinyl chloride and the foamed cushion layer20 is reheated to about 300° F. to about 450° F. so as to melt the uppersurface of the composition. The outer wear layer 22 then is applied tothe foamed cushion layer 20, such as by being pressed between rollers 40and 42 concurrently with the integral foamed cushion layer 20 and fabricbase layer 14. The resulting treadmill belt 12 is cooled to securelyadhere the outer wear layer 22 to the foamed cushion layer 20 and theneventually cut to desired lengths for use with treadmill 10. Prior touse, it will be understood that opposing ends of cut lengths of thetreadmill belt 12 must be combined together by techniques known in theart, such as finger splicing or bias splicing, or step splicing or skivesplicing for two or more plies, and heating together, to provide thecontinuous treadmill belt 12 of FIG. 1.

In another embodiment, a method of making the treadmill belt 12 of FIG.2A includes further applying, such as by placing, the fabricintermediate layer 28 on the unfoamed thermoplastic composition. Next,like layer 32, one or more layers of the second unfoamed thermoplasticcomposition is applied to the fabric intermediate layer 28. Then, thefirst and second unfoamed thermoplastic compositions are foamed by wayof a physical or chemical foaming agent, as discussed above, to definefirst and second foamed cushion layers 20, 30 which have a Shore Ahardness of about 20 to about 80.

Alternatively, the fabric intermediate layer 28 is applied to foamedcushion layer 20 then layer 38 of the second unfoamed thermoplasticcomposition is applied to the fabric intermediate layer 28. Next, thesecond unfoamed thermoplastic composition is foamed to define the secondfoamed cushion layer 30 which has a Shore A hardness of about 20 toabout 80.

By way of example, the second unfoamed thermoplastic composition caninclude the polyvinyl chloride composition of Table 1. As discussedabove, the azidocarbamide chemical foaming agent is heated to betweenabout 300° F. to about 450° F. to decompose the foaming agent and foamthe composition. In addition, the fabric base and intermediate layers14, 28 may be one-ply woven sheets of multifilament polyester.

Finally, the outer wear layer 22 is applied to the second foamed cushionlayer 30, as explained above, to define the treadmill belt 12 of FIG. 2Awith first and second foamed cushion layers 20, 30. In one example, theouter wear layer 22 includes polyvinyl chloride. The treadmill belt 12subsequently may be cut to length and spliced together. Accordingly,there is provided a treadmill belt with a cushioned layer that is easyto manufacture, not too thick, and provides the needed durability andshock absorbing characteristics to help prevent injury to the user.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. For example, rather than use the treadmill belt on atreadmill, the treadmill belt may be used in the light conveyor beltindustry as a conveyor belt. The invention in its broader aspects istherefore not limited to the specific details, representative productand method and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope of the general inventive concept.

1. A method of making a treadmill belt having a first foamed cushionlayer and a second foamed cushion layer comprising: applying at leastone layer of a first unfoamed thermoplastic composition on asubstantially non-extendable fabric base layer; foaming the firstunfoamed thermoplastic composition to define the first foamed cushionlayer which has a Shore A hardness of about 20 to about 80; applying afabric intermediate layer onto the first foamed cushion layer; applyingat least one layer of a second unfoamed thermoplastic composition ontothe fabric intermediate layer; foaming the second unfoamed thermoplasticcomposition to define the second foamed cushion layer which has a ShoreA hardness of about 20 to about 80; applying an outer wear layer ontothe second foamed cushion layer to define the treadmill belt with thefirst foamed cushion layer and the second foamed cushion layers; andsecuring a bottom surface layer to the underside of the fabric baselayer, wherein the bottom surface layer is comprised of polyurethane,wherein the outer wear layer is comprised of natural rubber or asynthetic rubber, wherein the first foamed cushion layer has surfaceswhich are exposed on the edges of both sides of the belt, and whereinthe second foamed cushion layer has surfaces which are exposed on theedges of both sides of the belt.
 2. The method of claim 1 whereinfoaming the first unfoamed thermoplastic composition comprises heatingthe first unfoamed thermoplastic composition to foam the first unfoamedthermoplastic composition to define the first foamed cushion layer, andwherein foaming the second unfoamed thermoplastic composition comprisesheating the second unfoamed thermoplastic composition to foam the secondunfoamed thermoplastic composition to define the second foamed cushionlayer.
 3. The method of claim 1 wherein the first unfoamed thermoplasticcomposition is an unfoamed polyvinyl chloride composition.
 4. The methodof claim 3 wherein the second unfoamed thermoplastic composition is anunfoamed polyvinyl chloride composition.
 5. The method of claim 1wherein the first unfoamed thermoplastic composition is comprised ofpolyvinyl chloride and a foaming agent, wherein the foaming agent ispresent at a level of about 1 part by weight to about 5 parts by weightper 100 parts by weight of the polyvinyl chloride.
 6. The method ofclaim 1 wherein the fabric base layer is a one-ply woven sheet ofsynthetic and/or natural material, and the outer wear layer includes athermoplastic material or a rubber material.
 7. The method of claim 1wherein the first unformed thermoplastic composition and the secondunfoamed thermoplastic composition are simultaneously foamed to definefirst foamed cushion layer and the second foamed cushion layer.
 8. Themethod of claim 1 wherein applying at least one layer of the firstunfoamed thermoplastic composition on the fabric base layer comprisesdirectly applying at least one layer of the first unfoamed thermoplasticcomposition on the fabric base layer; and wherein applying an outer wearlayer on the foamed cushion layer to define the treadmill belt withfirst foamed cushion layer comprises applying an outer wear layerdirectly onto the foamed cushion layer to define the treadmill belt. 9.A treadmill belt comprising: a substantially non-extendable fabric baselayer; a first foamed cushion layer foamed on and integral with thefabric base layer, the first foamed cushion layer including a firstfoamed thermoplastic composition and having a Shore A hardness of about20 to about 80; a fabric intermediate layer securely adhered on thefirst foamed cushion layer so as to sandwich the first foamed cushionlayer between the fabric base layer and fabric intermediate layer; asecond foamed cushion layer foamed on and integral with the fabricintermediate layer, the second foamed cushion layer including a secondthermoplastic composition and having a Shore A hardness of about 20 toabout 80; the outer wear layer securely adhered on the second foamedcushion layer so as to sandwich the second foamed cushion layer betweenthe fabric intermediate layer and outer wear layer thereby defining thetreadmill belt; and a bottom surface layer which is secured to theunderside of the fabric base layer, wherein the outer wear layer iscomprised of natural rubber or a synthetic rubber, wherein the firstfoamed cushion layer has surfaces which are exposed on the edges of bothsides of the belt, wherein the bottom surface layer is comprised ofpolyvinyl chloride or polyurethane, and wherein the second foamedcushion layer has surfaces which are exposed on the edges of both sidesof the belt.
 10. The treadmill belt of claim 9 wherein the first foamedthermoplastic composition is foamed polyvinyl chloride.
 11. Thetreadmill belt of claim 9 wherein the fabric base layer is a one-plywoven sheet of synthetic and/or natural material, and the outer wearlayer includes a thermoplastic material or a rubber material.
 12. Thetreadmill belt of claim 9 wherein the first foamed cushion layer is fromabout 0.05 inches to about 0.35 inches thick and wherein the secondfoamed cushion layer is from about 0.05 inches to about 0.35 inchesthick.
 13. The treadmill belt of claim 9 wherein the first foamedcushion layer is a solid material and wherein the second foamed cushionlayer is a solid material.
 14. The treadmill belt of claim 9 wherein thebottom surface layer is comprised of polyurethane.
 15. A method ofmaking a treadmill belt having edges on both sides of the beltcomprising: (1) applying at least one layer of a first unfoamedthermoplastic composition on and integral with a substantiallynon-extendable fabric base layer; (2) foaming the first unfoamedthermoplastic composition to define a first foamed cushion layer whichis a solid material that has a Shore A hardness of about 20 to about 80,wherein the first foamed cushion layer is from 0.05 inches to 0.35inches thick, and wherein the first unfoamed thermoplastic compositionis a polyvinyl chloride composition that includes 100 parts of polyvinylchloride and 1 part to 5 parts of a foaming agent per 100 parts ofpolyvinyl chloride; and (3) applying an outer wear layer on and integralwith the foamed cushion layer to define the treadmill belt; wherein theouter wear layer is comprised of natural rubber or a synthetic rubber,wherein the first foamed cushion layer has surfaces which are exposed onboth sides of the belt; and (4) securing a bottom surface layer to theunderside of the fabric base layer, wherein the bottom surface layer iscomprised of polyvinyl chloride or polyurethane, and wherein saidtreadmill belt consists solely of (1) the fabric base layer, (2) thefirst foamed cushion layer, (3) the outer wear layer, and (4) the bottomsurface layer.
 16. The method of claim 15 wherein the first foamedcushion layer is free of semi-solid substances.
 17. A treadmill beltcomprising: (1) a substantially non-extendable fabric base layer; (2) afirst foamed cushion layer foamed on and integral with the fabric baselayer, the first foamed cushion layer being comprised of polyvinylchloride which is in the form of a solid material having a Shore Ahardness of 20 to 80, wherein the first foamed cushion layer is from0.05 inches to 0.35 inches thick; (3) an outer wear layer securelyadhered on and integral with the first foamed cushion layer so as tosandwich the first foamed cushion layer between the fabric base layerand outer wear layer thereby defining the treadmill belt with firstfoamed cushion layer; and (4) a bottom surface layer which is secured tothe underside of the fabric base layer, wherein the bottom surface layeris comprised of polyvinyl chloride or polyurethane; wherein the outerwear layer is comprised of natural rubber or a synthetic rubber, whereinthe first foamed cushion layer has surfaces which are exposed on bothsides of the belt, and wherein said treadmill belt consists solely of(1) the fabric base layer, (2) the first foamed cushion layer, (3) theouter wear layer, and (4) the bottom surface layer.
 18. The treadmill ofclaim 17 wherein the first foamed cushion layer is free of semi-solidsubstances.
 19. The treadmill belt of claim 17 wherein the fabric baselayer is a one-ply woven sheet of synthetic and/or natural material, andthe outer wear layer includes a thermoplastic material or a rubber.